At present, verification experiments of driving safety support systems (hereinafter referred to DSSS [Driving Safety Support Systems]) have been carried out so as to prevent traffic accidents caused by carelessness of drivers, which occur at intersections and on approach roads to the intersections.
The DSSS, for example, are systems which provide to a driver a traffic condition around the driver in the form of information that may be visually and acoustically recognized (such as a display of an alerting image or an output of an alerting voice message) and calls attention to a dangerous factor. Relaxed driving is thereby supported.
The DSSS include a transmitter (hereinafter referred to as an optical beacon unit) that transmits an optical signal, a transmitter (hereinafter referred to as a DSRC beacon unit) that transmits an electric wave of a 5.8 GHz band, an apparatus on a road side (hereinafter referred to as an information relay and determination apparatus) including a roadside control unit (information relay and determination device), an in-vehicle unit that exchanges data with the optical beacon unit and the DSRC beacon unit.
The DSSS further include a sensor (hereinafter referred to as a detection sensor) including a vehicle detection sensor and a pedestrian detection sensor, and a signal controller (hereinafter referred to as the signal controller), as apparatuses on the road side. The DSSS include a function of detecting position information, speed information, the number of vehicles, and the number of people detected by the vehicle detection sensor and the pedestrian detection sensor. The vehicle detection sensor detects distances of a four-wheeled vehicle and an automatic two-wheeled vehicle from an intersection and running speeds of the four-wheeled and automatic two-wheeled vehicles as they enter into the intersection. The pedestrian detection sensor detects a pedestrian walking on a crosswalk within the intersection and a bicycle on the crosswalk. The signal controller controls a traffic flow at the intersection. The roadside control unit collects intersection signal information from the signal controller and the information detected by the detection sensor, and transmits those information to the optical beacon unit and the DSRC beacon unit.
The optical beacon unit is installed before the intersection. The optical beacon unit transmits the position of a lane on which the vehicle is running and provision of a DSSS service. The optical beacon unit provides to the vehicle static information (hereinafter referred to as fixed information) such as geographical information on the size of the intersection, presence or absence of a side road, through the in-vehicle unit that has received an optical beacon.
The roadside control unit (information relay and determination device) collects information on the position of an oncoming vehicle entering into the intersection and the speed of the oncoming vehicle and information on the presence of the pedestrian or the bicycle on the crosswalk within the intersection, detected by the detection sensors. The roadside control unit further collects information on the color of a traffic light output from the signal controller. The roadside control unit thereby prepares traffic (intersection) information that changes real time and transmits the traffic (intersection) information to the DSRC beacon unit.
The DSRC beacon unit is installed in the vicinity of the intersection, and provides to the vehicle the traffic information that has been prepared by the roadside control unit and changes real time.
Using the above-mentioned DSSS, a right-turn accident prevention service and a left-turn hit accident prevention system at an intersection, for example, have been evaluated and verified.    Patent Document 1: JP2007-219588A